xii CONTENTS 
CHAPTER IV 
SEX INHERITANCE 
PAGE 
The Drosophila or XX-XY Type .............. 78 
The Abraxas or WZ-ZZ Type .........+.004 83 
What are Sex Factors? «200... fe 90 
Hermaphroditism and Sex .... . Pge kes . 94 
Parthenogenesis and Sex . . . 97 
The Sex of Individuals Produced by: Artificial Parthenopanesis 106 
Sex and Secondary Sexual Characters : ooh. 106 
Parasitic Castration and Secondary Sexual Characters .. .. 114 
Gynandromorphs and Sex . B00 eee se red tae ee 116 
Intersexes and Sex ' gh ie! Gal AD ag 124 
Triploid Intersexes in Drosophila RivlanGeaston ee ae ee ee eee 130 
Sex and Sex-determining Gametes ...... ....... 132 
Sex-ratios. . . 2... Wo Meera a & : ogo DBA 
CHAPTER V 
THE CHROMOSOMES AS BEARERS OF HEREDITARY 
MATERIAL 
The Evidence from Embryology ia Bo) ee RAG 141 
The Individuality of the Chromosomes . . ¢ a 2 2S 
The Chromosomes during the Maturation of the Germ Cells i . 155 
Crossing Over. . . : se «ee «4 164 
Other Theories of Crossing-over ’ ‘ sa as 168 
Attachment of Sex-chromosomes to Ayitasmmes fe ware dae AS 
Tetraploidy : 5 Rh, ie Gl denies ter Boe ep SA 174 
CHAPTER VI 
CYTOPLASMIC INHERITANCE 
The Self-perpetuating Bodies in the Cytoplaam ... ... 182 
CHAPTER VII 
THE CORRESPONDENCE BETWEEN THE DISTRIBUTION OF 
THE CHROMOSOMES AND OF THE GENETIC FACTORS 
Parallelism between the Distribution of Chromosomes and of Factors 187 
1. In Cases of Normal Distribution. Bo) Ai he Haye t 187 
